The purpose of this project is to study the use of minor sports injuries as proxy measures for more serious athletic injuries in late adolescence. We aim to assess whether: 1) individuals with major injuries have more minor injuries than those without major injuries; 2) major injuries are preceded by minor injuries; 3) specific types of minor injuries are associated with specific types of major injuries; 4) periods of vulnerability to minor and major injuries can be predicted by periods of stress; 5) medical records are reliable and valid indicators of individual's injury experience. Methodological issues which will be examined include: 1) a definition of minor injuries which will be most predictive of major injuries (i.e., a comparison of severity ratings based on restricted activity, level of treatment, tissue damage); 2) the length of the time period during which minor injuries occur that best predicts major injuries (i.e., are major injuries preceded by a cluster of minor injuries the week before, the two weeks before the occurrence of the major injury, the month before the major injury?); 3) the reliability of self-reported injury data resulting in medical treatment. We propose to study the association between minor and major injuries at the United States Military Academy at West Point (USMA). The USMA offers a unique opportunity to study this issue because of a highly controlled and uniform environment, the centralized provision and recording of health care, a high frequency of athletic injuries, the ability to collect self-report data directly through terminals at each cadet's desk, and the strong interest the military has in injury prevention. Three study designs will be employed: 1) a retrospective cohort study of the medical records of 1400 cadets who entered the academy in 1988, followed over their four year cadet careers; 2) a one year retrospective cohort study of the records of cadets who played intramural football in 1991 (N = 700), 3) a one term prospective study of 100 cadets in intramural football. Survival analysis will be used to study the association between minor and major injuries. If we can demonstrate that minor athletic injuries are associated with major injuries, either in general, or for specific anatomical sites, researchers will be able to formulate and test hypotheses about processes which link injuries of different severity, and will be able to quantify, the effect of preventive interventions aimed at minor injuries on the rate of severe injuries.